More misc. tweaks and cleanups

Notable changes:

.github/workflows/ci.yml:
- Run 'bin/package test' on the github runner so we test iffe too.

src/cmd/ksh93/sh/subshell.c:
- sh_assignok was usually called like 'np = sh_assignok(np,0)'. But
  the function never changes np, it just returns the np value
  passed to it, so the assignment is pointless and that function
  can be changed to a void.

src/cmd/ksh93/sh/fault.c: sh_fault():
- Remove check for sh.subshell after sh_isstate(SH_INTERACTIVE). As
  of 48ba6964, it is never set in subshells.

src/cmd/ksh93/edit/history.c

@@ -1,7 +1,7 @@
 /***********************************************************************
 *                                                                      *
 *               This software is part of the ast package               *
-*          Copyright (c) 1982-2012 AT&T Intellectual Property          *
+*          Copyright (c) 1982-2014 AT&T Intellectual Property          *
 *          Copyright (c) 2020-2022 Contributors to ksh 93u+m           *
 *                      and is licensed under the                       *
 *                 Eclipse Public License, Version 1.0                  *